What are the Polar Coordinates and Speed of a Car on a Straight Road?

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SUMMARY

The discussion focuses on calculating the polar coordinates and speed of a car traveling at a constant speed of 65 mi/hr along a straight road. The user initially miscalculated the radius, assuming it to be 100 ft, which led to incorrect results for the angular velocity (theta with dot above) and radial velocity (r with dot above). The correct approach involves using the equations Vr = v cos(theta) and Vtheta = r * theta (with dot above) to derive the necessary values accurately.

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  • Familiarity with trigonometric functions, particularly cosine
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  • Proficiency in applying kinematic equations for circular motion
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krnhseya
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Homework Statement



A car P travles along a straight road with a constant speed v = 65mi/hr. At the instant when the angle theta = 60 degrees, determine the values of r (with dot above) in ft/sec and theta (with dot above) in deg/sec. (r = 100ft)

The picture has a car on highway and radius pointing diagonally from the origin which is on the field in "/" like this.

Homework Equations



Vr = r (with dot above)
Vtheta = r*theta(with dot above)
v = sqrt(((Vr)^2)+((Vtheta)^2))

The Attempt at a Solution



Vr = v cos theta and found Vr without a problem.
I tried to plug in v = 65mi/hr (converted to ft/sec) into 3rd eqn with Vr in order to find Vtheta. After that I substitude it into 2nd eqn since I know the radius. I got the theta value and converted to deg/sec from rad/sec but I am not getting answer.

What mistake have I made? :(

Thank you.
 
Physics news on Phys.org
What is the position of the car relative to the origin, and what direction is it moving in?
 
wow, i just made the stupidest mistake ever...
i JUST realized that radius is NOT 100 hahaha
sorry about that! and thank you!
 

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